Well-pipe clamping apparatus



Feb. 9, 1932.

s. LJCAMPBELL.

WELL PIPE CLAMPING APPARATUS Filed March 12, 1927 2 Sheets-Sheet 1 Feb.9, 1932.. 5.. L. CAMPBELL 4, 7

WELL PIPE CLAMPING APPARATUS Filed March 12. 1927 2 Sheets-Shunt 2 $.92.51; if 74/ WA #6 i298. fi 2,,

latented Feb. 9, 1932 UNITED STATES PATENT OFFICE STEW'ART L. CAMPBELL,F BERKELEY, CALIFORNIA, ASSIGNOR TO JOHN GRANT, OF

LOS ANGELES,

CALIFORNIA Application filed March 12,

This invention has to do generally with devices For clamping about andsupporting ver- 'lrally iiltending worlc, and is more particularlyconcerned with means for supporting well-pipe such as isinp drill stemor tubing in a manner to suspend such work from the annual surface.

"this device, as is typical of all devices of the heel nature describedabove, includes a p all I oil? wedge slips arranged to be nizu illtl) lout of clamping engagement will th worn, the slips in turn being suppirl ed. when in worh engaging position, in a manner to hold the work insuspension. 1 As is well known to those skilled in the art,

in the operation of usual clamping devices it i 1 necessary actually toraise the work-load in order to role the slips from clamping lent withthe work. In contradistinciiill' 1e upper end of the. string, beingsuphy an elevator and l'ioisting tackle. 1 won the clevatmhoisted toraise the whole on until the load is taken oil the slips. The slips arethen lifted out of place by hand and the entire string lowered until itsupper just above the clamping means, wherethe slips are reinserted aboutthe pipe the string lowered in a manner to wedge the slips into clampingengagement thereo; eral'ions thw equire actual raising ch time the slipsare released and ividual movement oil the sllps each 1927. Serial No.174,775.

time they are to be drawn clear or reinserted. "the above operations arenot only laborious andtime and energy consuming, but also neccssitateextreme care in order to prevent accident. For instance, in lowering theslips about the pipe, it is necessary that there be at least two men tohandle the. slips, and they must drop the slips simultaneously in orderto check the descent of the string at the proper time, improper droppingof the slip often resulting disastrously both to the equipment andworkers, as is well understood by those skilled in the art.

My provision for releasing the load without 'aising it eliminates manyof the steps men tioned above and generally increases the efficiency ofclamping devices to a marked degree and with obvious advantage.

So far as I am aware clamping devices having this characteristicofload-release Without load-lift, have been provided in but one otherinstance, such a device being the subject-matter of a patent issued toJohn Grant, April 6, 1926, No. 1,580,099 on releasable spider. Thefollowing difference, however, exists between the device shown in thepatent and the device now under consideration. In the patent, the slipsare allowed to move away from the work without lifting the latter, byvirtue of drop ping the slip-supporting ring away from the slips, whileholding the slips up, so that the slips are free to move radiallyoutward and clear of the pipe; there is involved a momentary transfer ofthe load thrust from the sup porting ring to the slips themselves byvirtue ol the lowering of said supporting means. In the present device,the sllps are allowed movement away from the pipe without such loadtransfer by virtue of the slip-supporting means being mounted formovement radially outward from the pipe, or, in other words, by beingbacked ol'l' horizontally from the pipe. To allow for this, theslip-supportin means is made up of units movable individua ly withrespect to the main or body member support of the device. he slips andthe slip supporting means may each be considered as a radiallyexpansible and contractible ring of elements about the work, and Iprovide means for moving them positively toward the work,

said means being releasable in order that the rings may be allowed freemovement radially away from the work, at the will of the operator.

An important feature of such slip movement resides in the fact that theslips may be swung or moved over the body support in a manner fully toclear the work-taking bore, it following that the slips do not haveto belifted out or reinserted manually, as is true of usual clamping devices,thus reducing the labor and time of each clamping and unclampingactuation to a minimum, and eliminating the danger of loose slips; aboutthe ring. This danger is a real one, as it is a matter of somewhatcommon occurrence for loose slips to be accidentally'kicked into thewell bore, thus entailing costly fishing jobs.

Furthermore, the means for radially contracting the rings is such thatall the slip elements may be moved either inwardly or outwardlysimultaneously, it thus being assured that downward movement of the pipemay be checked at the proper instant and that the individual slipelements are rendered fully releasable at the same instant.

l/Vhile my invention is applicable to any type of body support such asusual spiders mounted stationarily over the well bore, it may be used toparticular advantage in connection with rotary tables. This advantage isgained both by reason of the fact that the slips and the slip-supportingmeans may be used alternately with the usual driving bushing withouthampering the efliciency of either and because the power normally athand for rotating the table during boring operations may be applied mosteffectively to the means for alternately moving the slips to the workand allowing them freedom of movement away from the work. However, thispoint may be discussed more fully and to better advantage in thefollowing detailed specification, wherein further objects and novelfeatures will be made apparent.

Reference will be had to the accompanying drawings in which: i

Fig. 1 is an elevation of a device embodying my invention shown inconnection withrconventionally illustrated hoisting means for the work;r r

Fig. 2'is an. enlarged plan section on line 22 of Fig. 1; r

. Fig. 3 is a section on line 33 of Fig. 2;

Fig. 4 is a section on line 4:4: of Fig. 2; 1 Fig. 5 is a view similarto Fig. 2 butshowing the slips in clamping position;

Fig.6 is a section on line 6-6 of Fig. 5;

Fig. 7 is a fragmentary sectionon line 77 I of Fig. 5;

Fig. 8 is a fragmentary section on line 8-8 of Fig. 5;

Fig.- 9 is a fragmentary view showing a variational form ofslip-support;

Fig 10 is a section on line 10l0 of Fig. 9;

nation, it is not a limitation on certain aspects of the invention, forit may as well be adapted to apparatus utilized solely for supportingwork, for instance, a spider.

In the drawings I have shown a supporting body generally indicated at 10and including a ring-shaped base 11 mounted on sills l2 and supporting arotary table 14 for rotation about a vertical axis. The table is adaptedto be revolved in the usual manner from power shaft 15 through bevelgears 16, 17,

the latterbeing provided on the underside of the overhanging rim 17a ofthe table. Preferably, though not necessarily, at the upper end ofsleeve portion 18 of the table, which portion preferably has peripheralhearing at 19 in base 11, there is provided a bushing 20 having anannular'flange 21 at its upper end. This bushing has tight fit withinthe table and the upper face of its flangeis substantially flush withtable-topQQ; consequently,'the bushing rotates with, and may be broadlyconsidered as a part of, the table and the upper face of flange 21 maybe con sidered as a partof the table face.

The table has a vertically extendin axial bore 23 adapted to take workW. In Figs. '1, 2 and 3, wherein the slips are shown free of the work orin inoperative position, work W is in the form of a well-pipe supportedfrom above by elevator E in engagement with the pipe collar C. Theelevator, in turn, is suspended by bails B from a hoisting hook H, usualtackle (not shown) being utilized for hoisting or lowering away theelevator in the usual manner.

Mounted for substantially horizontal movement on top the table areprovided a plurality of slip-supporting members or carriers 24, saidcarriers being movable substantially radially with respect to the axisof bore 23 over the table-top. I have shown and will describe theparticular type of and mounting for the carriers, and will also describea particular method of applying wedge slips to saidcarriers. However, itis to be distinctly understood that the invention, considered in itsbroader aspects, is in no way limited to the particularities set forth,for they are specified merely that a thorough understanding may be hadof a preferred construction, from which may be gained knowledge of theprin-- ciples of the broadly considered invention. For instance, broadlyconsidered, the invention contemplates the movement of theslipsupporting means as movable substantially radially with respect tothe work axis into and out of engagement with the work. The means forguiding the members through the predetermined path of movement may be ofany suitable nature and still lie within the scope of the invention,though I have here shown a mounting wherein the carriers are adapted tobe pivotally connected to the table for oscillatory movement towards andaway from said axis. Nhile, in following their paths of oscillatorymovement, the carriers do not travel exactly along radii extended fromthe work axis or the axis of the work-taking bore, they substantiallyfollow such radii and, therefore, for the purposes of description and ofthe claims, they may be considered as moving substantially thercalong.This view will be taken throughout the remainder of the description aswell as in the accompanying claims.

Since the individual supporting members or carriers 2% may be identicalwith one another and since their mounting may be the same, I willdescribe but a single carrier and its mounting in detail. A givencarrier 24 may be considered as an arm or lever pivoted on the table forhorizontal oscillatory movement thereover mat a pivot pin 25, said pinsprcterably bein naked in sockets 26 whereby they may be easily removedfrom assembly with the table. As will be hereinafter made apparent, pinsalso serve as driving connections between the table and the slipcarriers. the carriers, through their pivots 25, mounted directly onbushing flange 21, which is considered as a part of the table.

The given arm 24, thus pivotally connected at 525 for horizontaloscillatory movement, has at opposite sides of its free end 28, or, ex-

r pressed otherwise, at a point along its axis spaced from its point ofpivotal connection, a cam nose 29 with an arcuate cam face 30 which issubstantially concentric with bore 23 or the axis of rotation of work V,and a downwardly and in ardly inclining wedge '0. 211 which issubstantially arcuate, as wed in plan. Pin 25 is so located and arm Ellis of such effective length, that oscillatory movement of the arm movesits free end substan i: lly radially with respect to axis A of bore 2?and work W.

Mounted on carrier 2% is segmental wedgeslip 32, the outer arcuate wedgeface 33 there of inclinii'ig inwardly and downwardly and beingsubstantially complementary to carrier face 31; while the opposite,substantially vertical face 34 is preferably serrated or toothed at inthe usual manner in order to present a proper pipe engaging or grippingst are. tillip segment has an outwardly extending horizontal flange 86which overlies and is normally vertically spaced from the top face 37 ofcarrier 24, a bolt 38 extending with loose fit at 39 through the flangeand into connection at 40 with the carrier. A

compression spring 41 encircles bolt 40 be tween the underside of theflange and face 37, tending yieldably to hold the slip at its upperlimit of travel along the bolt, which limit is established by thedownwardly facing shoulder presented by the head of the belt. a

It will be seen that due to the engagement of wedge fa es 231 and 33,downward movement of the slip with relation to the carrier is adapted tomove the slip radially with respect to the carrier toward axis A, theloose lit between the bolt and slip-flange allowing such movement.

The several pivot pins 25, or centers of oscillation of the individualarms, are arranged in a circle about axis A and are spaced angularlyfrom one another. Therefore, with the slips movable simultaneously andradially inwardly or outwardly toward or from axis A, the severalcarriers taken together as a group and the several slips taken togetheras a group may be considered as rings of elements arranged about axis Aand capable of substantially radial contraction and expansion, the ri'gs being radially contracted to bring the slips into engagement with thework and then being capable of radial expansion away from the work.

lit is thus apparent that the individual slips and their carriers aremovable horizontall y toward and away from the work without verticalmovement. This is in direct c011- tradistinction to foregoing deviceswherein the slips are movable radially from the Work only by virtue ofprior relative vertical movement between the slips and their supportingmembers.

lVhile any suitable means may be provided. for radially contracting thering of slips and then allowing its radial expansion, 1 have shown aparticular means which is preferable due to its simplicity and generaleffectiveness, 21 single member being adapted to cause equal andsimultaneous inward movement of the slips and to release all. of saidslips simultaneously to allow them to have outward radial movement. Forthis purpose, I provide a cam ring 42 which mounted on the table top soas to be capable of relative rotation with respect thereto. \Vhile themanner of supporting this ring and holding it "from lateral displacementis not controlling on the invention, I have here shown the ringposition-ed horizontally by the upturned marginal, annular flange -ll ontable 14-, which flange takes the ring with sliding fit within its bore.l Vhile it is not essential, I also preferably provide releasable meansfor holding the ring against upward vertical displacement, said meansbeing formed conveniently by passing bolts ll through flange 48 into theannular groove provided about the periphery of the ring. The bolts, ofcourse, have loose fit with the ring so they-do not tend to bind sameandinterfere with its free rotation.

Ring 42 is provided with inwardly-extend ing cams 46, there being onecam for each carrier 24, and the several cams being spaced apartangularly and equally thus providing relieved portions or recesses 47between each cam'and the next one on each side thereof. The majorextents 48 of the inwardly presented cam faces are arcuate, as viewed inplan, and, complementary to nose faces 30. Preferably, though notnecessarily, faces 48 are substantially concentric with bore 23 or withthe axis of rotation of work W and are of appreciable angular extent andextending from the defining faces of recesses 47 to faces 48 are theinclined cam faces 49, though the drop-off. ends of the cams which willbe at one side or the other thereof depending upon the direction ofrotation of the table may be relatively abrupt, as indicated at 50.

Cams 46 and recesses 47 are so arranged that when the carriers are inthe positions of Fig. 2, slips 32 are well clear of or backed away fromwork w l while, when the ring and table are relatively rotated to thepositionof Fig. 5, cam noses 48 have ridden up inclines 49 in a mannerto force the carriers radially inward to bring the slips into engagementwith the work, and as long as faces or noses 29 are in engagement withcam faces 48, the supports and slips are held from outward radialmovement from such operative position and the slip carriers and cam ringmay be considered as self locked in operative positions.

As a convenient means for setting uprelative rotation between the camring and table I provide a stationarily supported post 51 on one of thesills 12, and a radially extending lug 52 on ring 42. Either, or boththe pin and lug (which form, in effect, coacting shoulders on the silland ring) may be moved from operative position when occasion arises forusing the table without the slips. It will be seen that with lug 52 inengagement with till post 51, the ring is held against rotation in aclockwise direction, as viewed in Figs. 2 and 5, when the table andhence the supporting members and slips are moved in said directlon byvirtue of rotation of drive shaft 15, pins 25 providing a driveconnection between the table and carriers 24 whereby the latter aredrawn circumferentially about axis A during the described movement ofthe table. It follows, that step by step rotation of the table throughangles of predetermined extent, alternately causes the carriers to moveradially inward to bring the slips into engagement with work of givendiameter and to hold them against outward-radial movement and then toremove the backing (cams 46) from behind the carriers so they are freeto move the slips'radially outward from engagement with the work. Itwill be obvious that it requires only a partial revolution of the tableto move the carriers completely and simultaneously inward or to releasesaid carriers simultaneously so they may be backed horizontally awayfrom the work. 1

Before describing the releasable means preferably provided for limitingthe angular extent of table movement during certain phases of operation,I will set forth a typical operative cycle of the device.

First assume that the elements be in the position indicated in Figs. 1,2 and 3, and that the load of pipe W be taken entirely by elevator E. Inthis condition, the slip carriers are backed away sufficiently to holdthe slips out of operative engagement with the work, it following thatsprings 41 are holding the slips in their uppermost position (Fig. 3).If it now be desired to clamp the work to relieve the load from theelevator, the table 14 is rotated to bring carriers 24 into the positionof Fig. 5. The inward radial movement ofthe carriers forces the slipsradially inward into engagement with pipe W. The elevator E is thenlowered away and the pipe, by virtue of its frictional engagement withthe slips, augmented by the serrated faces 34 of the latter, serves tocarry the slips clownwardly toward or inwardly into the position of Fig.6, this movement wedging the slips tightly between the carriers and pipeby virtue of the coaction between wedge faces 31 and 33. This wedgeaction contracts the ring of segmental slips closely about and intoclamping relation with the pipe so the pipe load is thereafter taken bythe supporting member and table through the slips, whereupon theelevator may be-freed from the work. Of course, springs 41, due to theirinterposition between faces 37 and flanges 36, in their compressed statelimit the downward movement of the slips with relation to theirsupporting members. i

When occasion arises for releasing the slips from the pipe, at whichtime the pipe load is adapted again to be supported by an elevator,table 14 is rotated in a manner to bring noses29 into radial alinementwith recesses 47, or, expressed otherwise, oif cams 46. The backingbehind carriers 24' then being removed, the carriers are free to moveradially outward away from the-work; The clamping assembly, consideredas a whole, has been put under such strains of radial compression inbeing clamped to the pipe, that as soon as said compression strains arerelieved by reason of the carriers clearing cams 46,the clamping unitsmove radially to expanded position, and springs 41 return the slipelements to raised position.

Generally, the release movement may be described as movement of thecarriers and slips substantially radially outward from axis A, or as ahorizontal backing. away of the slip supporting means from the work. 'Itwill be noted that the slips and slip supports are movable to radiallyexpanded position without the necessity of relative vertical movementbetween them and the table, or of relative vertical. movement betweenthe slips and slip-carriers.

It is desirable. though not necessary, that mean. he provided .o preventaccidental or inadvertent over-rotation oi the table when it is intendedto clamp the slips to the work. In other words, as the table rotated tocarry nlembers 2i from the position 0t Fig. 2 to that of Fig. 5, it isdesirable that releasable means be employed for preventingthe table frombeing rotated accidentally to an extent carrying members 24.- past camsa6 and thereby allowing; the slips to loosen their hold on the workbefore such release is intended.

its a convenient, releasable means for limiting the extent 0t ai'lgularmovement o1 the table in being; l'fiijtllfitl from slip release positionto gripping position, I provide a pawl or detent on one of the rotatableelements, tor instance, on one ot' the carriers. This pawl is mounted onthe v1rrier-supported shaft 56 t'or movement about a horizontal axis,and is adapted to extend radially from said carrier in a manner tooverlie the top of ring 42. np ularl and equally spaced about ring 42are inns 57 which present shoulders 58 facing in a direction oppositethat of table-rotation, there being one shoulder to each carrier member.The shoulders are so positioned that pawl is in engagement with one ofthem (Figs. and 8) when the supporting members are in full contact withcams lG. It follows that the table cannot be rotated beyond thisposition to bring the carriers into alinement with rcce t'i' until pawl55 has been swung upwardly clear of the cam shoulder this actionrequiringwillitul effort on the part of the operator. The pawl isadapted to drop back to the position of Fig. 7 as soon as it released bythe operator so it is in position to engage the succeeding stop shoulder58 when the ible is rotated to bring the slips next into work-grippingrelation. To forestall efforts on the part of the operator to avoid thesafety feature of pawl by rotating it about hull-i all to a positionfrom which it will not drop into operative association with. shoulders58, I provide a heel member 59 on the pawl which projects rearwardly orinwardly from shall: 56 and is adapted to enthe upper 'lace oil' thecarrier in a manit the ctlective end of the pawl 'ungr to vertical orbeyond ver to i never on. 9, l0 and, ll 1 have shown a slight red typeof slip and carrier assembly. arrier 2hr generally similar to carrier 24l k and is mounted on the tatile-carried post 25 in the same mannerthereon. in this variation, however, slip 3964 has on its rearwardinchucd taco 33a a central longitudinally EX- tending lug or guide 84awhich is arcuate, as viewed in horizontal cross-section and of greaterangular extent than 180. This lug mounted for longitudinal slidingmovement through the complementary bore a in carrier Ella. the lug andway inclining at the same angle as do the faces 86a. and 33a of thecarrier and slip, respectively. The slip is thus mounted forlongitudinal movement with respect to the carrier and has wedge-faceengagement therewith in a manner similar to that described in connectionwith faces 31 and 33. The com plementary arcuate character stics ot lugs34 and way 35a hold the slip :t'rom horizontal displacement with respectto the carrier. l

There provided a spring 37a anchored at one end 38:: to member 24a andengaging at its free end a downwardly facing shoulder 89o provided onlug 340:. This spring serves normally and yieldably to hold the slip inits uppermost position, downward movement of the slip being definitelylimited by engagement oi? the underside of horizontal flange lilo withthe upper face of member 24a. It will be apparent that the slip and itscar 'ier function in precisely the same manner as do the slips andcarriers heretofore described.

In order to produce roller engagement between carriers 2% and cams 46,with the obvious object of reducing frictional resist ance, I mayprovide for each carrier a roller which is mounted on carrier shaft 61for rotation about a vertical axis. However, for the sake of simplicity,I have shown but one carrier so equipped. This roller is so positionedthat it adapted to take the thrust of cams it when the carrier is movedinto alincment therewith and has rolling contact with cam face 48during, operation of the device (it eours this feature of rollingcontact may be embodied in the slips previously described.

In order that the table fashioned in accordance with the abovedescription may be utilized for drivingly supporting the nut or drivebushing whereby the usual drill stem (not shown) is rotated, Withoutcalling for material re-adjustment of parts, carriers 24 are preferablyreadily detachable from the table. For instance, the driving connectionmay be such that the carriers may be merely lifted oil pins 25. Thenwhen occasion arises tor using the table for boring purposes, theslip-supports and either or both post 51 and lug 52 are removed.Thereupon, the split drive nut or bushing generally indicated at 62(Fig. 12) is installed in place of the slips. Ring 1-2 may or may not beremoved for it does not interfere with the placement and operation ofthe drive bushin This drive bushing is preferably made up of twocomplementary parts 63 and 64, each part comprising a horizontal plateportion 65 from which extend wings 66, the latter being apertured at 67to take drive pins 25.

The opposed faces 68 of parts 63, 64:, are cut out centrally to form avertical passageway 69 which is polygonal, as viewed in plan, andproportioned to take a usual kelley or grief pipe whereby drive isadapted to be transmitted from the table to the drill stem (not shown).Plate portions are adapted to rest on top face 37 and they may have,considered together, a centering hub 7 0 adapted to fit within bore 23.

It will "be obvious that the drive nut may be lowered into or liftedfrom operative engagement with the table with ease and dispatch, thesubstitution of the slips for the drive bushingbeing made with equalfacility. It follows that the apparatus may be adjusted quickly andeasily for alternate use as a pipe supporting or pipe rotating means,pins 25, in both instances, serving as the drive connective means.

It will be understood the drawings and description are to be consideredmerely as illustrative of and not restrictive on the broader claimsappended hereto, for various changes in design, structure andarrangement may be made without departing from the spirit and scope ofsaid claims.

' I claim:

1. In a device of the character a rotatable supporting body having avertical bore adapted totake work, a plurality of slips supported on thebody for movement substantially radially towards and away from the axisof the bore, and means actuated by virtue of step-by-step rotation ofthe body in a given direction for alternately moving the slipssubstantially radially towards the bore axis into work engaging positionand freeing them for movement substantially radially out of workengaging position.

2. In a device of the character described, a supporting body having abore adapted to take work, a plurality of slips supported on the bodyfor movement substantially radially towards and away from the axis ofthe bore, a member associated with the body for rotation with respectthereto, and means actuated by virtue of step-by-step relative rotationof the body and member in a given direction for alternately moving theslips sub stantially radially towards the bore axis into work engagingposition and freeing them for movement substantially radially out ofwork engaging position.

3. In a device of the character described, a supporting body ringthrough which work may pass, slip carriers mounted on the body ring forsubstantially radial movement to and from the work, wedge slips on thecarriers adapted to grip work by virtue of downward movement relative tothecarriers, a cam ring surrounding the carriers and having portionswhich extend radially inward and present cam faces concentric with theaxis of the work, said cam ring having other cam described,

faces which extend outwardly from said concentric faces, all in a mannerwhereby the cam ring is adapted by virtue of relative rotation of thecam and body rings to move the carriers in toward the work when saidother cam faces engage the carriers and to hold said carriers in whilesaid concentric faces engage the carriers, and means for applying powerto one of the rings to rotate it relative to the other ring.

4. In a device of the character described, a supporting; body ringthrough which work may pass, slip carriers pivotally mounted on the bodyring for swinging movement to and from the work, wedge slips on thecarriers adapted to grip work by virtue of downward movement relative tothe carriers, a cam ring surrounding the carriers and having portionswhich extend radially inward and present cam faces concentric with theaxis of the work, said cam ring having other cam faces which extendoutwardly from said concentric faces, all in a manner whereby the camring is adapted by virtue of relative rotation of the cam and body ringsto swing the carriers pivotally in toward the work when said other camfaces engage thecarriers and to hold said carriers in while saidconcentric faces engage the carriers, and means for applying power toone of the rings to rotate it relative to the other ring.

5. Ina device of the character described, a horizontal rotary tablewhich is centrally apertured to take vertically extending work, slipcarriers pivotally mounted 011 the table for horizontal swingingmovement to and from the work, wedge slips on the carriers adapted togrip workby virtue of downward movement relative to the carriers, a camring surrounding the carriers and having portions which extend radiallyinward and present cam faces concentric with the work, said ring havingother cam faces which extend outwardly from said concentric faces, allin a manner whereby the cam ring is adapted by virtue of relativerotation of the ring and table to swing; the carriers pivotally intowardthe work when said other cam faces engage the carriers and to hold saidcarriers in while said concentric faces engage the carriers, and meansfor holding the ring against rotation while the table is rotating.

6. In a device of the character described, a rotatable supporting bodyhaving a vertical bore adapted to take work, a plurality of slipspivotally supported on the body for horizontal swingingmovement towardsand away from the axis of the bore, means actuated by virtue ofstep-by-step rotation of the body in a given direction for alternatelyswinging the slips horizontally towards the bore into work engagingposition and freeing them for movement radially out of work engagingposition.

7. In a device of the character described,

lit]

a rotatable supporting body having a vertical bore adapted to take work,a plurality of sl' supported on the body for movement 5 ibstantiallyradially towards and away :l rom the axis of the bore, means actuated byvirtue o't step-bvstep rotation of the body in a given direct n foralternately moving the slips substantially radially tom rds the boreinto work engaging position and freeing them for nniveinentsubstantially radially out of work engaging position, and releasablemeans for holding the siuiporting body against rotation in said givendirection.

in a device of the character described, a summrtin body ring tnroughwhich work may pass, work clamping members mounted on the body ring forsubstantially radial moven'ient to an d from the work, a cam ring :-:urrmnding ill members and having portitms which extend radially inward andpresent cam faces (ZOIlL'KDtI'lC with the axis of the work, said camring having other cam faces which extend outwardly from said concentricfaces. all in a manner whereby the cam ring is adapted by virtue ofrelative rotation (Ill the cam and body rings to move said members intoward the work when said other cam tacos engage the members and to holdsaid members in while said concentric tacos engage the members and meansfor applying power to one of the rings to rotate it relative to theother ring.

9. in a device of the character described, a supporting body ringthrough which work may pass, work clamping members pivotally mounted onthe body ring for swinging movement to and from the work, a cam ringsurrounding the members and having portions which extend radially inwardand present cam iaces concentric with the axis of the work, said camring having other cam faces which extend outwardly from said concentricFaces, all in a manner whereby the cam ring is adapted by virtue ofrelative rotation of the cam and body rings to swing said membore intoward the work when said other cam Faces engage the members and to holdsaid members in while said concentric faces enthe members, and means forapplying power to one of the rings to rotate it relative to the otherring.

10. in a device of the character described, a supporting body rinthrough which work may pass, a cam ring associated substantiallyconcentrically with the body ring, work clamping membr-a's within. thecam ring, pivotal connections between the body ring and nu'embers, saidcam ring being adapted by rotation relative to the body ring to engagethe members and thereby swing them at their giivotal connections intoward the work, and means for applying power to one of the rings torotate it relative to the other ring.

ll. In a device of the character described, supporting body ring throughwhich work may pass, a cam ring associated substantially concentricallywith the body ring, work clamping members within the cam ring, pivotalconnections between the body ring and members, said cam ring beingadapted by rotation relative to the body ring to engage the members andthereby swing them at their pivotal connections in toward the work, saidpivotal connections being circumferentially offset from the points ofcam and ring engagement, and means for applying power to one of therings to rotate it relative to the other ring.

12. In a device of the character described, a supporting body ringthrough which work may pass, a cam ring associated substantiallyconcentrically with the body ring, a series of angularly spaced camportions extending radially inward from the cam ring, work clampingmembers within the cam ring and movable substantially radially intoengagement with and away from the work, means drivingly connecting saidmembers to the body ring, and means for holding said cam ring stationarywhile the body ring is rotated, a given clamping member being engageablesuccessively with the cam portions when the body ring is rotated in agiven direction, and said cam portions each being adapted to engage andmove said clamping member into engagement with the work.

In witness that I claim the foregoing I have hereunto subscribed byname.

STEWART L. CAMPBELL.

